3dz2 electron orbital, illustration. An electron orbital is a region around an atomic nucleus (not seen) in which one or a pair of electrons is most likely to exist. The 3dz2 orbital has a unique shape resembling two lobes elongated along the z-axis with a doughnut-shaped region (or torus) around the nucleus on the x-y plane. The orbital is seen transparent at middle to show the axes of symmetry and the conical nodes can be seen at right. Nodes are the regions in an atom with zero electron density and where the electron is least likely to exist. For the 3dz2 electron orbital, 3 indicates that it is the third energy level, and d indicates that the orbital is specifically a d-orbital, and (z2) indicates that the lobes of the orbital are oriented along the z-axis. The 3dz2 orbital can accommodate up to 2 electrons. It is part of the 3d shell, which contains five orbitals in total. The 3d orbitals are part of the 3 shell, which also contains one spherical 3s orbital and three bi-lobed 3p orbitals, both at a lower energy (not seen).